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Re: Aquatic Plants Digest V3 #262

Alysoun McLaughlin asked:

> Second question -- and I tried to read the archives on this, but have you
> ever tried to search under "slow growth" or "slow"?
> I had incredible growth when I set this tank up (two or three months ago),
> but in the past few weeks, my growth has been slow -- in fact, nothing seems
> to have been growing at all for the past week or so.   It's not because of
> digging them up last weekend (see my earlier post about substrate bubbles),
> because this was a problem before then.  I also have a problem (with hygro
> species) with roots that seem to be sprouting from the middle of the plant.
> Could this be because of:
> 1)  A nutrient deficiency?  I haven't seen a description that seems
> appropriate on any of the charts that I've found in the archives.

It's fairly common to see rapid growth in a new tank, followed by a slower
growth after things settle down.  I can think of several non-problems that
might cause that.  Without some symptom other than slow growth there may
be no nutrient problem or maybe there is a problem and it just isn't acute

> 2)  Related to my substrate bubbles?

If the bubbles are nitrogen as Steve Pushak suggested then it means that
nitrate in the substrate is being converted by bacteria to nitrogen gas.
Plants need nitrogen, but they can't get it from nitrogen gas, so this
removes nitrogen that could otherwise be used by the plants.  Under some
conditions that could contribute to slower growth, but if you have
measurable nitrate in the tank, then it probably isn't the problem.

> 3)  A result of something else I haven't considered?  I have new lighting (a
> coralife 10,000K and an aquaglow) on the tank, but no CO2 injection (I'm
> hesitant to set up a soda bottle contraption, and certainly don't intend to
> drop the cash on a commercial system, but I'll set it up if I discover that
> my plants require it).  I have had pH fluctuation problems in the past, but
> it's been steady at about 6.5 for the past few weeks.

The primary controls on plant growth rates in aquariums probably are light
levels and CO2 availability.  The light output from a new flourescent
light can drop pretty fast for a while after you buy it, and that can
cause plant growth to slow down.  Also, if you don't add extra CO2 your
plant growth rate will be limited by how quickly CO2 can get into your
tank from more natural sources. If that slows down then so will the

I'm surprised that a planted tank with no added CO2 would have a pH of
6.5.  Is that higher or lower than it used to be?

Also, slow growth isn't necessarily a problem.  Slower growing plants need
less pruning and demand less attention to nutrient supplies.  The down
side is that algae and damage from any source tend to accumulate over time
and the older leaves on slow growing plants can sometimes get pretty

As to the hygro roots...

Its pretty normal for h. polysperma to grow roots from mid-stem.  I don't
think that's diagnostic of any problem.  I think the roots are
unattractive.  After a while I got tired of pruning them off and just
chucked the plants in favor of more civilized inhabitants.

Roger Miller